In a broadcast encryption scheme, a content distributor encrypts its privileged content for users or clients who are listening on a broadcast channel or a distribution network. Any user or client can use his private key to decrypt the encrypted content received, but only the chosen subset of users or clients can decrypt the encrypted content into the original content. The content distributor can control and select for this subset. Broadcast encryption has several applications including access control in encrypted file systems, television subscription services, and media content protection.
Traditional broadcast encryption schemes, such as those using Public Key Infrastructure (PKI) or bilinear pairings, create cryptographic headers that grow proportionately with the size of the user population or subscriber base, or the total number of clients in the distribution network. Since the cryptographic headers are sent along with the encrypted content to the users or clients, it causes network performance degradation when the total user population is exceedingly large, and also as the subscriber base grows.
Therefore, there is a need for a new broadcast encryption scheme such that the cryptography headers are of constant sizes regardless of total user population and changes in the subscriber base.